Stealteam4 Ching,

What brand is your kt150 power amp

check pm drchan.

I have bought brandnew KT150 integrated tube amp from Meixing few months ago,

and found it does not sound good, I think all transformers
are not good enough.

I have modified several amplifiers upgrade to KT150 for others R33 members with difference brands and found Jadis is one of the best sounding.

Richard

最後修改時間: 2016-02-01 15:04:39

hello richard,

is it kt150 sound very bright and thin ?
is it suitable to replace it into my melody kt88 amp ?

do i need to change tubes of 12ax7 and 6sn7 if i
change to KT150 tubes ?

i need warm sound in vocal and musical sound in instruments.


thanks

Dear hk005,

The KT150 will improve the overall sound quality of any KT88 pushpull amplifier, 100% OK.

Due to the large power of KT150, you may set the bias current of KT150 higher than KT88 subject to the power transformer output, then the sound will become warm and powerful.

I have tried in several KT88 amplifiers, including Jadis, Audio Research, etc..

No need to change tubes of 12AX7 & 6SN7.

Dr. Richard Chan



最後修改時間: 2016-04-16 14:01:43

Has anybody try the KT150 on CJ's power amp?
MV60SE or the ART power.

I recently bought one Jadis Orchestra Reference with KT90 tubes,

after testing for several days, I immediately want to upgrade to KT150

because my previous upgrades for replacing EL34/KT88/KT90/KT120 with KT150

all found sound improve dramatically,

the next item to concern is the bias current for KT150

the existing setting for KT90 made the amp total power consumption only 120watts

and I found the power transformer is about 500watts, I expect that I can adjust the bias for KT150 up to 250watts total power consumption.

I will upload details in next few days after modification and adjustment completed.

Richard Chan



最後修改時間: 2016-06-23 18:56:51

The first step is measure the existing total power consumption
by KT90 tubes and found about 115watts.

Open the chassis and replace all KT90 by KT150 and adjust the voltage across
each 5.9 ohm resistor close to 0.4Vdc, then the bias of KT150
will be around 68mA (the maximum plate current for KT150 is 275mA)

The revised total power consumption is about 212 watts after replaced
all KT90 with KT150, the maximum power transformer of Jadis Orchestra is
about 500watts, the 212 watts (42%) can be operated continously without
any overheat problem.

The maximum power output per channel is about 50watts after replacement.



最後修改時間: 2016-06-24 09:37:56

Photo with KT150

The cost of one quad set of Tung-Sol KT150 is about HK$2000

But the sound improvement worth over HK$20,000



最後修改時間: 2016-06-24 10:13:15

#111
Open the chassis and replace all KT90 by KT150 and adjust the voltage across
each 5.9 ohm resistor close to 0.4Vdc, then the bias of KT150
will be around 68mA (the maximum plate current for KT150 is 275mA)

******************************************************************************

Pls indicate whether there is any VR to adjust the bias or we need to change to reistor as mentioned above?

Thank you.



最後修改時間: 2016-06-24 11:30:28

There is one VR at the socket of each power tube.

You do not need to change any existing resistors inside the chassis.

Dr. Chan



最後修改時間: 2016-06-24 11:47:25

#111. 那個陰極電阻，如果沒看錯色環是[綠藍紅]的話，它的阻值是5.62Ω而不是5.9Ω。若其兩端的電壓被調至0.4V的話，則流過它的電流是71.1mA而不是67.8mA。

再者，光將靜態徧流調大，沒錯會令粍電量(亦即發熱量)增加，但若不同時増加陽極電壓，則不見得會將輸出功率，從40W(按官網所示規格)増大至50W。
http://www.jadis-electronics.com/en/orchestra-reference-51.php

小弟以上淺見，如有錯的話，請師兄指點更正，謝謝！

The actual resistance measured is 5.9 ohm instead of 5.6 ohm

secondary, if we increase the bias current without increasing the working voltage, the output power is depend on P=IV and will increase some watts purely due to increase current.

furthermore the original bias for KT90 is too small for KT150

by the way, do you have one unit of Jadis Orchestra on hand under modification?

最後修改時間: 2016-06-24 13:56:40

The maximum working temperature is about 42C after replacement with KT150

#117
1. 5.62Ω的電阻，從色環上看是1%誤差值的，除非使用日久或因過熱變值，否則它不會變成5.9Ω的。
2. 用普通的萬用表來量低阻值電阻，一般得岀的讀數，都會較實際阻值為大，這是因為沒有將表針引線電阻，和接觸點電阻考慮進去。如果使用毫歐表及Kelvin leads，則讀數會精確得多。
3. 你調整徧壓可變電阻後，量度陰極電阻兩端電壓，所計算出來的，是靜態電流，亦即是既沒有輸入也沒有輸出的靜態耗電功率。這耗電功率，跟擴音機的最大輸出功率，完全是兩回事，兩者之間，甚至連成正比例的關係都沒有。正如石機甲類功放，其靜態耗電量大(亦即發熱量大)，但輸出到喇叭的功率就(不成比例地)並不大。P=IV是沒錯，但如那I只是靜態電流(而不是最大輸出時的電流)，那麼計算出來的P，也只是靜態(沒有訊號被放大)時的P。它與擴音機的最大輸出功率，並無關連。

我並沒有Jadis膽機需要摩改升級，但若要將輸出功率從40W增大至50W，除了換輸出膽之外，尚要更大的推動電壓(以Jadis orchestra為例，每聲道只用一支雙三極管作前級電壓放大，和分相，未免有點乏力)，更高的陽極電壓，更大的供電電流，和更大功率的輸岀牛。沒有全套整體來配合，只靠調高輸出級的靜態電流，是沒可能將輸岀功率增大的。

When you really got one unit of Jadis Orchestra on hand,

you will find there is one step FET amplifier in the input

the 50watts output after replace with KT150

can be measured by input signal generator

with dummy load plus oscilloscope.

#121. 原來如此，那FET是甚麼編號呢？

Please Check PM Dr Chan